Protecting Aluminum Boats From Salt Water Corrosion
By: Boating Magazine
In the last 5 years, boaters have bought over 300K boats.
Aluminum boats require special care to prevent salt water corrosion.
They’re light, economical, nearly maintenance-free, easy to repair and almost impervious to damage. The Coast Guard and Navy prefer them for small craft, and many commercial boats are aluminum, as are many recreational craft. Their high strength-to-weight ratio means they can be built lighter and therefore can run faster for a given amount of power, and are easier to trailer. If you’re looking for the ideal boat building material, aluminum could be it. The only problem is that it’s the wimp of the electrochemical schoolyard, being beaten up and corroded away by almost every other metal except for zinc and magnesium.
Want to be a saltwater metal head? Aluminum can seemingly dissolve away in salt water when in the presence of other metals. Builders do everything they can to prevent this, but once the boat is in your hands it’s up to you to keep it alive. Here’s how.
How It HappensWe’re talking about galvanic corrosion. Back in science class you’d say that this is where one metal in an electrically conductive solution (such as salt water) gives up atoms when connected to a dissimilar metal in that same solution. Losing atoms means that the metal is falling apart, or corroding. In the slip aboard your aluminum boat, you’d say that this is where your hull becomes pitted because of a bronze through-hull on a neighboring boat.
The rate of corrosion of a metal on its own is determined by how chemically active it becomes when put in salt water. The more active, the more susceptible it is to corrosion. The less active, the more resistant it is to corrosion. When not in contact with anything else, most marine metals such as aluminum, bronze and stainless steel will corrode away at a reasonably slow rate. No danger there. But connect different metals, one active (aluminum) and the other a lot less active (i.e., a copper penny), in water and atoms will start to flow. And the aluminum will start to fall apart.
The Good NewsWhen not in contact with other metals, aluminum can do quite well in both fresh and salt water, needing only bottom paint to prevent fouling. However, to play it safe, the American Boat and Yacht Council (ABYC) recommends that “aluminum vessels shall have a protective paint coating that provides a high [electrical] resistance barrier between the aluminum and the water.”
Above the waterline aluminum does even better. When continuously exposed to oxygen, it develops a film of aluminum oxide so dense and well bonded to the metal that it prevents further corrosion. That’s why many commercial and military craft leave aluminum bare from the waterline up: There’s no need for protective paints, cosmetics aside. As you can see, building an aluminum boat for salt water takes thought. The right alloys must be used, welding must be done just right, and parts must be carefully assembled.
Fiesta, a Florida pontoon builder that bills its boats as “built for use in salt water,” isolates hardware and stainless-steel bolts from the aluminum with nylon washers. Hull compartments have drains with silicone-sealed nylon plugs that can be opened to drain accumulated moisture. They also employ dedicated mounting brackets for sacrificial anodes, and their hulls and extrusions are made from thicker metal.
Better aluminum boat builders don’t allow crevices or joints that collect water, and avoid upturned brackets and channels that trap water. Moisture, including condensation, must drain away, with no sealed or dead air spaces. An emphatic spokesman for Premier Pontoons said, “We are constantly doing pre-emptive detective work to stop corrosion before it starts.”
Zinc or SwimEngine manufacturers, as well as boatbuilders, attempt to save their aluminum products by attaching sacrificial anodes. As long as the anode is electrically connected to the part, either by direct contact or by wire, it stuffs the aluminum with excess electrons so it loses those rather than the aluminum giving up its own electrons. The zinc? It erodes — sacrificing itself for the benefit of the boat or motor.
Unfortunately, there is no formula to tell you how many anodes you will need and what size. In the beginning, it will be a matter of trial and error. A good place to start is the ABYC’s procedure. Inspect the anodes every month. Go with many small ones rather than a few large ones. If you have the right amount, your “zincs” should be about halfway gone by the end of the season, and replaced each spring. If they are not wearing away, they are either too large (rare) or not making good contact with the aluminum (common). Well-made anodes should have cast-in plates and fasteners to maintain good electrical connection throughout their lives, and they should meet military spec Mil-A-18001J (or higher last letter).
Don’t go nuts with zincs everywhere because aluminum won’t tolerate being overprotected. In mild cases, the zinc develops a crust and stops working. But if things get too far out of balance, you can generate an alkaline solution that will start eating away at the aluminum. An early sign of this is the softening or blistering of the bottom paint.
How Much Zinc?
Use too few anodes, and the fittings are not protected. Use too many, and the anodes erode quickly and may blister paint. A multimeter and a reference electrode help to nail down the right amount.
1. Place a silver/silver chloride electrode in the water near the item that is to be protected.
2. Touch the positive probe to the fitting. Note the meter’s reading in DC millivolts.
3. Connect a sacrificial zinc of the proposed size to the metal part to be protected. Put the zinc in the water and note the new meter reading.
4. Protection is adequate when the new voltage is 200 millivolts (0.20 volts) more negative than the reading noted without the zinc.
The Trouble with Tanks
Even if you don’t have an aluminum boat, you probably have aluminum fuel tanks. While these can be perfectly safe, the U.S. Coast Guard noticed a recurring problem with leaking tanks. So it asked Underwriters Laboratory to see why. Not surprisingly, UL found that corrosion caused 92 percent of the failures. Most of it was caused by how the tanks were installed.
In general, aluminum tanks should be left bare. Paint can help. But if it’s not properly applied, it wears away, scratches or peels off, and moisture gets under the paint, concentrating and accelerating corrosion.
The most common fittings used in fuel systems are usually made from brass. Screw one of these directly into an aluminum tank and add some moisture, and you’ve got serious galvanic corrosion. Isolate these fittings from the tank by using 300-series stainless-steel washers or adapters.
The tank’s supports must not be moisture-absorbent, such as carpeting is. Suitable materials are stiff neoprene, Teflon or any high-density plastic. Water should drain from all tank surfaces when the boat is at rest; the bottom of the tank must be at least a quarter-inch above the hull to let air circulate and above the level normally reached by bilge water. The European standard says “no less than 25 mm [1 inch] above the top of the bilge pump inlet or the bilge pump automatic float switch.”
A fuel tank should be accessible for relatively easy inspection via a screwed-down, caulked hatch, but that is often not the case. Many builders install tanks so that a saw is needed for inspection or replacement. Too bad.
13 Ways to Prevent Galvanic Corrosion
1. Don’t mix metals, or at least use metals as close to each other as possible in the galvanic series.
2. Bolts should be less active than fittings; they’re small, so loss of metal is more serious.
3. Take all measures to electrically isolate fittings from each other, even on small craft.
4. Securely fasten anodes, and ensure there is firm contact with the metal to be protected.
5. Never paint an anode. Be sure the metal to which it is fastened is free of paint, scale and dirt.
6. Impressed current voltage should never exceed 1,300 millivolts when protecting aluminum.
7. Always repair paint chips and scratches that expose bare metal as soon as possible.
8. Avoid using any lubricant made with graphite aboard a boat made from aluminum.
9. Employ an isolation transformer whenever the boat’s connected to AC shore power.
10. Don’t use an automotive battery charger aboard a boat, especially an aluminum boat.
11. Paint only with primers and coatings specifically designed for aluminum.
12. Wash the aluminum boat down with fresh water after every use to remove built-up salts.
13. Keep hooks, sinkers, bottle caps and other metal debris out of the bilge lest they wreak havoc.
DIY the Right Way
Protecting your aluminum boat and equipment from the rigors of the marine environment.
Ideally, you’d use aluminum fittings and fasteners, minimizing the chance of galvanic corrosion, but these are hard to find. Instead use 300-series stainless steel. This works fine if you isolate the fitting with plastic washers or pads and keep the water out with a polysulfide or polyether bedding compound like Star brite polyether Boat Caulk.
Interlux and Pettit sell copper-free, aluminum-compatible paint systems backed by excellent application instructions and tech support. It takes lots of prep, plus attention to detail, to do this right.
Ditch Your Carpet
To prevent hull pitting caused by trapped moisture, replace carpeted trailer bunks with vinyl with DeckRite.
Tiki Bar Inspires Couple to Go Afloat on a Pontoon Houseboat
Sitting lakeside at your own private tiki bar, sharing drinks and steaks with your loved ones.
How can life get any better?
Jeff and Julia Kloeckner of Laingsburg, Michigan asked themselves that exact question one afternoon, and Jeff decided what the tiki bar needed was a houseboat.
I sat down one sunny afternoon recently to talk to the Kloeckners, my friends and neighbors. We sat on their back deck and enjoyed the view of the lake and their pontoon.
Jeff proudly talked about his pontoon and the story behind it, while Julia grabbed her photo album and displayed all the pictures documenting her husband’s boat creation.
The Pontoon Houseboat JourneyThe 1987 Manitou Pontoon was built at the original Delta Township factory, not far from Kloeckner’s home. It was sold to a family who took it up north to Gaylord, and they enjoyed it for many years, until the Kloeckners bought it from them in 2009.
When the Kloeckners purchased their pontoon, the recession was affecting gas prices so much that they soon found they used the boat less and less.
Their 18-foot, ’87 Manitou Pontoon had been sitting idle at the dock throughout the summer. The more it sat, the more Jeff pondered over what he could do with it.
He wanted to be able to use his pontoon for fishing and floating. Better yet, to turn it into a houseboat to enjoy at their location on Round Lake and take it to other lakes too.
Round Lake is known as Al Capone’s hideaway spot. The current Lakeview Banquet Center on the lake used to be a dance hall with big bands and bootleg booze.
Today Lakeview is a busy reception hall for weddings and other gatherings. Locals on the lake boat out near the hall to watch wedding ceremonies, listen to the music and take in the occasional evening firework displays.
Fireworks, beautiful sunsets and star-filled nights are just a few more good reasons a houseboat would be fitting on Round Lake.
Not only that, but Michigan has over 11,000 lakes to explore. There are so many different things to do in and around Michigan lakes. You can check out the “Lake Effect” at Pure Michigan.org and discover the endless opportunities of fun things to do and enjoy.
If you’re looking to camp on your pontoon or conversion pontoon, check out this pontoon camping guide.
The Kloeckner’s have known firsthand what lake life is all about and were ready to discover new adventures with their houseboat on Round Lake and other lakes up north. Thus, they began their own DIY pontoon houseboat project.
How to DIY Your Own Pontoon HouseboatLuckily, Jeff had the capability to configure his own houseboat design and structure.
His 30-plus years of construction experience and a jack-of-all-trades know-how gave him the confidence and skill to tackle this type of DIY project.
Less experienced DIY folks may want to use a kit to transform their pontoon. There are hundreds of ideas—some crazy!—that you can find online.
However, you really need to sit down and decide what you want for your houseboat, what will work for the size of your boat frame and the budget that you have to work with.
The possibilities can be endless!
What about adding a bathroom? Or a hot tub? Or even a second deck with a slide down into the water? The sky truly is the limit for just about anything you can imagine for your own houseboat.
Need some ideas? Go to Pinterest, type “conversion pontoons” in the search bar and you’ll discover an endless stream of pictures of the most amazing pontoon houseboats, and houseboats from around the world.
Once you choose your style, whether it’s simple or a floating Jimmy Buffet theme, build it with passion and keep safety in mind.
Some Takeaways: Consider Safety, Weight, Capacity and Insurance
Conversion projects like this bring up a number of questions on transforming a pontoon into a houseboat. One question for converting into a houseboat would be the framing structure and weight distribution.
The Manitou pontoon’s initial construction is ideal for strength and dependability. When you’re adding weight and height to the framework, you’ll just need some guidelines to keep it safe. The United States Coast Guard has a booklet to calculate your precise weight and capacity limits.
Manufacturers place a weight and capacity limit sticker on the boat at the factory. I called a Manitou dealer in Michigan and they recommended staying within the limitation that’s posted on the boat, for safety. Adding weight and height to a boat frame can make the boat unstable.
Another question would be insurance. Do you keep the same coverage for your boat as you would for a houseboat? I highly recommend contacting your own insurance agent to make sure you have the best coverage suited for your needs.
How to Expertly Use Recycled MaterialJeff created his houseboat using recycled material. Lansing’s Cooley Law Stadium, home of the minor league baseball team the Lugnuts, had just undergone major updates and Jeff was able to use the steel sides from the outfield storage unit.
The steel sheets were used as the sides of his 8′ x 10′ houseboat construction. He used steel studs for the framework to keep costs and weight down on the pontoon.
He also wanted the boat to be self sufficient, so he designed a way to use solar energy to power a Minn Kota Electric 55-lb thrust trolling motor. Jeff added a ceiling fan to the interior for cooling, installed sunglass material for the roof and placed house windows on the sides to also allow light and air flow.
A screen door in the front adds to the charm! And the inside has room for their queen-size air mattress (for when the fish aren’t biting) and storage for fishing equipment.
On the front of the boat, Jeff has two spots to insert fishing seats. He and his wife can comfortably sit, dangle their feet in the cool lake water and fish to their heart’s content!
What’s in a Name?
On the side of the boat Jeff added the boat’s name, Lily pad.
Fitting for floating on their small lake like… a lily pad! Jeff cut and designed lily pads from a steel metal sheet, painted the boat’s name on them and then attached them to the side of their houseboat.
When I asked them what they love best about the boat, they both replied that “it’s one of a kind!” Jeff loved working from his own ideas and how the solar unit helps keep their Lily pad self sufficient.
If you’re looking for recycled building material for your pontoon conversion, check out Habitat for Humanity. It’s a great place to look for recycled items for your project and help your community at the same time. Habitat stores are filled with building material, cabinets, furniture and so much more.
Think outside the box and find new treasures to go afloat!
- Amy Cabanas
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Memorial Day from Stem to Stern | Pontoon Depot
Memorial Day kicks off Boating Season at the Lake! A reprise of our Memorial Day Fun from last year’s celebration!! I hope you don’t mind weighing anchor with me again :-)
In anticipation of boating over the course of the long holiday weekend, I decorated the pontoon for fun. . .. . .from Stem to Stern. . .including a few stems in a mason jar!
A few pillows. . .
Some Red,White & Blue to dine with. . .
A beverage tub filled with drinks to keep us hydrated. . .
A breezy day as you can see, with the wind whipping the flags~
Of course Memorial Day has a much more important significance than boating & picnics. . . it commemorates U.S. soldiers who died while in military service.
First enacted to honor Union and Confederate soldiers following the American Civil War, it was extended after World War I to honor Americans who have died in all wars.
A day to recognize, reflect, and remember, how fortunate we are to live in freedom.
We’re celebrating with a flag formation of Watermelon, Feta, and a side of Blueberries~The creamy, salty cheese is the perfect partner to the sweet, juicy melon.However you celebrate, spend a few moments to remember and give thanks for those who serve & protect us . . .Wishing you a Safe & Happy Memorial Day!
Pontoon Boat Prep: Before the Season Starts…
If you’re like most pontoon boat owners, you’re itching to get back on the water once the season starts. If you don’t live somewhere with year round warmth, you may have stored the boat away for winter—but that doesn’t mean you can’t start preparing for the spring and summer season now!
Read on to see a few things you can do to get your pontoon boat ready for fun once the warmer weather rolls around.
As boat owners, we’re always looking for ways to make our next trip even better than the last. This might mean making improvements to your pontoon boat that make it more enjoyable for everyone on board. If you’ve been thinking about adding features such as a ladder, slide or tent cover to your boat, now is a great time to do it. By the time the season starts up again, your pontoon boat will be decked out and ready to go!
Clean up your pontoon boat and make necessary repairs
There are, of course, practical issues you may need to take care of during your offseason time. If there are any repairs you need to make on your pontoon boat, now would be a good time to check those out and pick up the necessary parts you may need. If all your boat needs is a bit of freshening up, devote an afternoon to cleaning it up and getting it back to looking like new.
Plan your next adventure
A fantastic way to keep yourself and your family occupied during the winter months is to plan your next adventure. Whether this is to a local spot or a bona fide vacation destination, everyone will enjoy having a say in the planning process. It’s also a great way to keep your mind focused on the water fun you’ll be having—without actually being on the water.
Give it a name
If you have not yet given your pontoon boat a name, do it this winter! Every boat needs a good name, both for practical reasons—so help on the water can find you easily, should you ever need it—and fun ones. Every pontoon boat has its own unique personality, just like the people who use it, so be sure to give yours a name that sticks.
Purchase your new pontoon boat
Like many boaters in search of a fun alternative to traditional powerboats, you may be considering purchasing a brand new pontoon boat this year. Why wait until the season’s already underway to do it? The winter months are the perfect time to think about the style and design you want and get your new boat ready for fun on the water in 2018.
If you fit into this category, get in touch with us today! We can make your pontoon boat wishes a reality in time for the season ahead.
Can’t wait to get back on the water? Try these ideas and hold on just a little longer—you’ll be seeing fellow boaters on your favorite waterways in no time at all.
- Amy Cabanas
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